Magnetic door catch



Feb 1, 1955 H. J. SCHMITT MAGNETIC DOOR CATCH Filed May e, 1954 UnitedStates Patent O MAGNETIC DOOR CATCH Howard J. Schmitt, Benton Harbor,Mich., assigner to Laboratory Equipment Corporation, St. Joseph, Mich.,a corporation of Michigan Application May 6, 1954, Serial No. 427,902

3 Claims. (Cl. 292-2515) The present invention relates to magnetic doorcatches of the type which comprises a permanent magnet secured to ashelf or door framework such that the magnet retains a door in closedposition by attracting an iron armature secured to the door.

One of the objects of my invention is to provide an improved magneticdoor catch of the type above described which is neat in appearance andwhich can be manufactured at extremely low cost.

An additional object is to provide a novel door catch of the typeindicated above which has a highly etiicient magnetic circuit and inwhich the elements are easy to fabricate and assemble.

Other objects and advantages will become apparent from the followingdescription of a preferred embodiment of my invention which isillustrated in the accompanying drawings.

In the drawings, in which similar characters of reference denote similarparts throughout the several views,

Fig. 1 is a front view of the permanent magnet portion of the magneticcatch and the housing and mounting provision therefor which forms thesubject matter of the present invention;

Fig. 2 is a horizontal, sectional view taken in a downwardly direction,as indicated by the arrows, along the line 2-2 of Fig. l in a positionjust within the top of the case. In this view the armature and itsrelationship to the remaining portion is also shown;

Fig. 3 is a side view of the door catch; and

Fig. 4 is a longitudinal, vertical sectional view which may beconsidered as taken in the direction of the arrows substantially alongthe line 4-4 of Fig. 2.

By referring to the drawings it will be apparent that the magnet case,indicated generally by the numeral 10, has a flat lower face as at 12,which is adapted for direct placement against a shelf or other frameworkjust within the door opening. The rearward portion 11 of the case memberis of thinner section than the remaining portion 13 thereof and forms amounting bracket. It is provided, as shown, with two longitudinallyslotted openings 14 through which screws can be passed for securing thecase in place.

The forward thick portion 13 of the case has a rectangular recess 16formed therein from the front face indicated at 18. As shown, thisrecess is approximately as deep as it is high and is of the order of oneand onehalf times as long as it is deep. These relationships are ofcourse not critical. The top and bottom walls 20 and 22, respectively,which form the recess 16, are perforated to provide aligned verticalopenings 24 and 26 which pass from the outside through the wall into therecess 16. These two perforations are located quite close to the frontface 18 of the housing, and are preferably along the center line of thehousing.

The entire case and mounting tab 11 as described above is formed in onepiece by any conventional process such as by plastics molding or diecasting for instance..

A good substance for the purpose is one characterized by reasonabletoughness and dimensional stability and some resiliency. Medium impactpolystyrene is well suited and relatively low in cost although othermaterials can of course be used. The use of a resilient substance hassome advantage during assembly, as will appear presently, and inaddition offers considerable protection to dishes and glassware whichmight be bumped against the magnet housing as they are inserted andremoved from the shelves.

Patented Feb. 1, 1955 Two magnet pole pieces are provided, and these areindicated at 28. They may suitably be formed of iron or low carbonsteel, and are simply cut from flat stock of appropriate thickness andformed to L shape, as shown. The two pole pieces are identical and havean over all length slightly greater than the depth of the recess 16 anda height which is slightly less than the similar recess dimension. Thesetwo pole pieces are dropped into the recess 16 with their longest atsides against the side faces of the recess as seen in Fig. 1, and withtheir bent-over ears 30 facing toward each other. These tabs are againstthe innermost face of the recess.

After these pole pieces are in place, a rectangular flat spacer member32 is dropped into the open mouth of the recess 16 so that it liesagainst the faces of the L-shaped extensions 30. This member cansuitably be manufactured at extremely low cost by being cut or punchedfrom ordinary cardboard. Its purpose is to prevent the magnetized memberfrom coming into direct contact with the inwardly extending ears 30.

The magnet member which is indicated at 34 is a cast slug, preferablyformed of one of the Alnico alloys. It is shown as a generallyrectangular bar section with two of the contiguous long edges beveled asat 36, but preferably with its two ends ground flat and parallel witheach other. Slugs of this shape are regularly cast as sticks or barswith deep score lines between the individual slugs. Thus individualslugs can easily be broken from the sticks along the score lines, thescore lines forming the beveling referred to above. Conveniently thegrinding operation is conducted before the bars are broken up.

The over all length of the permanent magnet 36 is slightly less than thedimension between the inside faces of the two pole pieces 28 when thesepole pieces are within the recess 16 and against the side walls thereof.The slug 36 therefore can be readily pushed into the mouth of thehousing between the pole pieces so that its back surface is against thespacer 32. The longitudinal dimension of the magnet 34 is not criticalsince the mag net will attract the pole pieces inwardly so as to providegood contact between its ends and these two iron members and theassembly of the pole pieces and magnet preferably has a loose iit in thecase in any event.

The remaining element is indicated at 38 and provides a closure for theopening between the pole pieces 28 and also serves to retain the magnetand pole pieces in the case. It is formed of nonmagnetic material andconveniently can be of any such substance having sufficient strength forthe purpose if a resilient case is provided. In general its contour isrectangular and its length is slightly less than the distance betweenthe inner surfaces of the pole pieces 23. Its height is equivelent tothe distance between the top and bottom walls of the housing. Itsthickness from front to back is slightly less than the distance betweenthe front face of the magnet 34 when it is in assembled relationship tothe other elcment and the front face 18 of the case. At its top andbottom edges, at the midpoints thereof, it has outward projections 40which t into thc holes 24 and 26. The front faces of these projectionsextend at right angles to the top and bottom edges of the member 38,whereas the back surfaces thereof are tapered inwardly and rearwardly sothat they merge with the top and bottom surfaces of the keeper orclosure 38.

If the keeper is rigid and the case resilient, the keeper is insertedsimply by locating it in front of the opening between the pole piecesand forcing it inwardly with an arbor press or the equivalent,therebycausing the tapered ends of the tabs 40 to wedge the top andbottom of the case outwardly so that the keeper moves inwardly into therecess until the tabs snap into place in the openings 24 and 26. When itis in place, with both of the tabs 40 located in their respectiveopenings 24 and 26, the keeper contines the magnet and pole pieceassembly slightly loosely.

If a relatively rigid case is provided, the keeper is preferably formedof a resilient plastic substance which will temporarily deform duringthe assembly operation, the assembly being conducted in substantiallythe manner indicated above.

With either type of construction, the outer ends of the polepieces 28project slightly beyond any portion either of the case or the keeper 38.No portion of the case, therefore, interferes with an armature 42 beingbrought into contact with these pole pieces, and therefore thelongitudinal dimension of the pole forming members need not beaccurately held with respect to the depth of the recess 16. It should benoted also that good contact is insured between the pole pieces 28 andthe magnet 34 without the necessity for welding these elements into asingle assembly and that the pole pieces and magnet are free to floatslightly Within the case so as to obtain good contact between thearmature and pole pieces even when a reasonable amount of misalignmentis present in the installation.

Although assembly of the device has been described above on the basis ofa step-by-step procedure, it will be appreciated that the pole pieces28, the spacer member 32, the magnet 34 and the keeper 38 can bepreassembled, the preassembly then being pressed into the case as aunit.

From the above description of a preferred embodiment of my invention itwill be appreciated that variations and substitutions can be madewithout departing from the scope or spirit of the invention, and thatthe scope of the invention is to be measured by the scope of thefollowing claims.

Having described my invention, what I claim as new and useful and desireto secure by Letters Patent of the United States is:

1. In a magnetic door catch, a resilient housing having a generallyrectangular recess therein and providing a means of attachment of thehousing to a surface, a pair of pole pieces formed of magnetic material,each of said pole pieces having an L shape to provide an outstandingportion and a shorter portion at right angles thereto, said pole piecesbeing disposed in said recess against the opposite sides thereof withtheir shorter portions against the bottom thereof and pointed towardeach other7 the length of said pole pieces being slightly greater thanthe depth of said recess, a flat resilient spacer member dis posed inthe space between the outstanding portions of said pole pieces andagainst said shorter portions, a bar magnet disposed with its ends incontact with the adja cent side faces of said pole pieces and in aposition against said resilient spacer member, a keeper disposed in saidrecess against said bar magnet and substantially filling the spacebetween said pole pieces, said housing and saidA keeper having mutualengaging means to retain said keeper in said recess, and said mutualengaging means operating to spread said housing when said keeper is partway into said recess, but to permit said housing to return tosubstantially its original form when said keeper is against said magnet.

2. In a magnetic door catch, a housing having a generally rectangularrecess therein and providing a means of attachment of the housing to asurface, a pair of pole pieces formed of magnetic material, each of saidpole pieces having an L shape to provide an outstanding portion and ashorter portion at right angles thereto, said pole pieces being disposedin said recess against the opposite sides thereof with their shorterportions pointed toward each other, the length of said pole pieces beingsucient to cause the outer ends thereof to extend t0 the opening of saidrecess, a spacer member disposed in the space between the outstandingportions of said pole pieces and against said shorter portions, a barmagnet loosely disposed with its ends in contact with the adjacent sidefaces of said pole pieces and in a position against said spacer member,a keeper disposed in said recess against said bar magnet and within thespace between said pole pieces, and means for retaining said keeper insaid recess.

3. In a magnetic door catch, a housing having a generally rectangularrecess therein and providing a means of attachment of the housing to asurface, a pair of pole pieces formed of magnetic material, each of saidpole pieces having an L shape to provide an outstanding portion and ashorter portion at right angles thereto, said pole pieces being disposedin said recess against the opposite sides thereof with their shorterportions pointed toward each other, the length of said pole pieces beingsufficient to cause the outer ends thereof to extend to the opening ofsaid recess, a spacer member disposed in the space between theoutstanding portions of said pole pieces and against said shorterportions, a bar magnet loosely disposed with its ends in contact withthe adjacent side faces of said pole pieces and in a position againstsaid spacer member, a keeper disposed in said recess against said barmagnet and within the space between said pole pieces, and means forretaining said keeper in said recess, said keeper when in retainedposition acting to retain said magnet, said spacer and said pole piecesloosely within said case so as to permit limited movement of said polepieces and magnet as a unit relative to said case.

References Cited in the tile of this patent UNITED STATES PATENTS2,508,305 Teetor May 16, 1950 FOREIGN PATENTS 631,523 Great Britain Nov.4, 1949

